The use of tubing and tubular members is ubiquitous in medical devices. In many tube-containing devices, such as intravascular catheters, the physical characteristics of the tubing are of great importance. For example, in catheters used in percutaneous transluminal coronary angioplasty (PTCA), the catheter tubing must extend from the patient's groin, through the femoral artery, over the aortic arch, into a coronary ostium, thereafter through tortuous vessel passages and into a secondary or tertiary coronary vessel within the heart. The tubing must be sufficiently flexible to track the often-tight turns through the vessels, yet capable of being pushed through the coronary vessels from a location near the groin. The tubing must also be capable of transmitting rotational forces applied near the groin into tip rotation near the heart.
The above requirements for catheters are often referred to as trackability, pushability, and torqueability. Meeting these requirements is complicated by a further requirement of having a small profile or outside diameter, so as to be able to pass through a small lumen, such as a remote coronary vessel of small inside diameter. Catheter tubing has often been made using variations of common tubing manufacture processes such as extrusion. Polymer is sometimes extruded over a mandrel, wrapped with wire or braid, and extruded over in a second pass, covering the braid. Such a process can impart a lubricious and/or strong inner surface, a strong intermediate braid, and a lubricious outer surface. The use of extrusion to form medical tubing commonly results in a homogenous tube wall consisting of melted polymer which is substantially uniform in orientation and composition.
What would be desirable is a simple method for making medical tubing that results in a tube having improved axial strength and pushability. It is further desired to have a method of manufacture in which the polymeric tube wall can incorporate varying or selected circumferential portions over the tube length with non-homogenous materials and properties. What would be further desirable is a method for making medical tubing having shapes and wall structures not possible using conventional extrusion methods.